On 2021/3/9 6:51, Alex Williamson wrote: > [Cc +Intel] > > On Mon, 8 Mar 2021 21:39:49 +0530 > Tarun Gupta <targu...@nvidia.com> wrote: > >> VFIO migration support in QEMU is experimental as of now, which was done to >> provide soak time and resolve concerns regarding bit-stream. >> But, with the patches discussed in >> https://www.mail-archive.com/qemu-devel@nongnu.org/msg784931.html , we have >> corrected ordering of saving PCI config space and bit-stream. >> >> So, this patch proposes to make vfio migration support in QEMU to be enabled >> by default. Tested by successfully migrating mdev device. >> >> Signed-off-by: Tarun Gupta <targu...@nvidia.com> >> Signed-off-by: Kirti Wankhede <kwankh...@nvidia.com> >> --- >> hw/vfio/pci.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c >> index f74be78209..15e26f460b 100644 >> --- a/hw/vfio/pci.c >> +++ b/hw/vfio/pci.c >> @@ -3199,7 +3199,7 @@ static Property vfio_pci_dev_properties[] = { >> DEFINE_PROP_BIT("x-igd-opregion", VFIOPCIDevice, features, >> VFIO_FEATURE_ENABLE_IGD_OPREGION_BIT, false), >> DEFINE_PROP_BOOL("x-enable-migration", VFIOPCIDevice, >> - vbasedev.enable_migration, false), >> + vbasedev.enable_migration, true), >> DEFINE_PROP_BOOL("x-no-mmap", VFIOPCIDevice, vbasedev.no_mmap, false), >> DEFINE_PROP_BOOL("x-balloon-allowed", VFIOPCIDevice, >> vbasedev.ram_block_discard_allowed, false), > > Looking back at the commit where this was added: > > commit cf254988a50d4164c86a356c80b8d3ae0ccaa005 > Author: Alex Williamson <alex.william...@redhat.com> > Date: Mon Nov 9 11:56:02 2020 -0700 > > vfio: Make migration support experimental > > Support for migration of vfio devices is still in flux. Developers > are attempting to add support for new devices and new architectures, > but none are yet readily available for validation. We have concerns > whether we're transferring device resources at the right point in the > migration, whether we're guaranteeing that updates during pre-copy are > migrated, and whether we can provide bit-stream compatibility should > any of this change. Even the question of whether devices should > participate in dirty page tracking during pre-copy seems contentious. > In short, migration support has not had enough soak time and it feels > premature to mark it as supported. > > Create an experimental option such that we can continue to develop. > > [Retaining previous acks/reviews for a previously identical code > change with different specifics in the commit log.] > > Reviewed-by: Dr. David Alan Gilbert <dgilb...@redhat.com> > Acked-by: Cornelia Huck <coh...@redhat.com> > Signed-off-by: Alex Williamson <alex.william...@redhat.com> > > > What has tangibly changed since then? I think we have patches on-list > to address the known issue of PCI config space (MSI) ordering, which > related to enabling migration on ARM platforms. Do we have > significantly more confidence in our ability to make compatible > enhancement to the migration bitstream? This was a particularly > troublesome point for me if we have any hope of calling this > supportable. As far as I know, there are still no open source vendor > drivers supporting migration for community testing. We're also still > missing the documentation that was promised previously, as Connie noted. > > Huawei and Intel, what's your confidence level and what can you share > regarding support for this implementation? Thanks,
We have sent a number of patches regarding VFIO migration from our own test (the support for this in our accelerator driver is still in experiment), some of them are still on-list []... [] https://lore.kernel.org/qemu-devel/20210310094106.2191-2-jiangkun...@huawei.com/ https://lore.kernel.org/linux-arm-kernel/20210126124444.27136-1-zhukeqi...@huawei.com/ Thanks, Shenming > > Alex > > . >
